DRM-less Amazon MP3 store now complete with Sony BMG

With the last remaining label of the big four to join the online retailer's new music store, it could be argued that DRM is essentially dead.

Last week, Sony announced its plans to go DRM-free. It did not name any distribution points at the time, although analysts speculated that Amazon would eventually carry Sony's content.

Prior to Sony, Warner was the most recent to join the service last month, with EMI and Universal joining earlier last year. Users will need to by a plastic stored value card in order to purchase music at select retailers.

All together, about 200,000 DRM-free tracks from Sony will be uploaded to Amazon MP3, meaning the total number of tracks on the service will reach 3.25 million. This is far more than iTunes, which only has about two million tracks.